Laser Flash Photolysis in High-Speed Photopolymer Coating Layers: Elucidation of Radicals Generated from Coumarin Dye-Sensitized Photoinitiator Systems

Abstract

Radical generation from photoinitintion systems containing carbonylbiscoumarin dye with a radical generating reagent, 3,3′-carbonylbis[7-(diethylamino)-2H-l-benzopyran-2-one](KCD-DA), with 2,22-bis(2-chlorophenyl),4,425,52-tetraphenyl-l,l2-bi-lH-imidazole (BI) in a poly(methyl methacrylate) (PMMA) film have been investigated by laser flash photolysis using a total reflection cell. The imidazolyl radical(lm·) was predominantly generated from a carbonylbiscoumarin triplet-sensitized decomposition of BI, where the quantum yield, Φ⁰_1m·, of lm-at an infinite concentration of BI was measured as Φ⁰_1m.,=0.5-1.4. The high quantum yield, Φ⁰_1m·, implies an efficient KCD-DA triplet sensitized photoinitiation system containing BI.